paul.f

As I expected, this is a known issue. It's already fixed in the Internet protection module version 1382, which is currently in testing.
Unfortunately it will take some time until it's released for your version of ESET Endpoint Antivirus. The fixed module will download automatically then.
Until that time, you can keep using the value of 443 for Ports used by HTTPS protocol; alternatively, you can try the less invasive change of the default value with the value of "443, 0-79, 81-65535" or "443, 0-79, 81-6567, 6569-65535"

This seems like an issue we are already aware of.
Please proceed as described here: https://support.eset.com/kb7272/ , but please enable Protocol filtering advanced logging as well. Don't forget to disable logging before Part II.
Then please send me the created logs via PM.
Then, you can try if changing this setting makes any difference:
F5 -> Web and email -> Web access protection -> Web protocols -> Ports used by HTTPS protocol
Change the current value (I expect there is 443, 0-65535) to 443.
We don't need any logs from the state when the setting is changed, at least for now.
Thanks.